I don't think this is anything serious to worry about. Young cats and kittens play rough and tend to damage their wiskers more often than mature cats do - however, with that being said, your kitty's whiskers should be at least as long as his face is wide (unless he is a hairless or curly coated breed). In other words, the tips of the whisker should extend to the edge of his cheeks.

Sometimes (rarely), broken and split whiskers can be an indication of poor nutrition or health problems. You are feeding a good diet, so that is not a problem. He may have worms that would prevent him from absorbing nutrients from his food, though, so having your vet give him a checkup would be worth the cost - if for no other reason than to set your mind at ease. In all likelihood, he is just fine, but even having the vet examine a stool sample may prove beneficial.